Currently, in situ cleaning of carpets and upholstery utilizes equipment for heating cleaning liquid that is conveyed under pressure to and sprayed onto the surface to be cleaned and then vacuum removed from the surface with the soil. This equipment is usually mounted in a panel truck, or van, for ease of transport and often includes the transport's internal combustion engine for driving the cleaning liquid and vacuum pumps.
As disclosed in co-pending U.S. patent application Ser. No. 10/329,227 filed Dec. 23, 2002 in the names of Wayne E. Boone, et al. for “DIRECT DRIVE INDUSTRIAL CARPET CLEANER,” the complete disclosure of which is incorporated herein by reference, typical industrial floor cleaning systems generally provide for the management of heat, vacuum, pressure, fresh and gray water, chemicals, and power to achieve the goal of efficient, thorough cleaning of different substrates, usually carpets but also hard flooring, linoleum and other substrates, in both residential and commercial establishments. Professional substrate cleaning systems are also utilized in the restoration industry for water extraction.
Of the many industrial substrate cleaning systems available, a major segment are self-contained having an own power plant, heat source, vacuum source, chemical delivery system, and water dispersion and extraction capabilities. These are commonly referred to as “slide-in” systems and install permanently in cargo vans, trailers and other commercial vehicles, but can also be mounted on portable, wheeled carts. Slide-in systems comprise a series of components designed and integrated into a package with an overall goal of performance, economy, reliability, safety, useful life, serviceability, and sized to fit inside various commercial vehicles.
FIG. 1 schematically illustrates one state-of-the-art industrial slide-in substrate cleaning system 1 (shown without scale) for carpets, hard flooring, linoleum and other substrates, one well-known example of which is the self-contained, gas-powered, truck-mounted model that is commercially available from Hydramaster Corporation, Mukilteo, Wash.
Typically, the components of a conventional slide-in carpet cleaner system 1 are structured around a frame or structural platform 2 onto which the majority of the components are mounted. The slide-in 1 typically includes a drive system 3 mounted on the platform 2 and having a power plant 4 coupled to receive fuel from an appropriate supply, a vacuum pump 5 that is the source of vacuum for removing gray water or soiled cleaning solution from the cleaned substrate, either carpet or other flooring, and an interface assembly 6 for transmitting power from the power plant 4 to the vacuum pump 5. The power plant 4 may be, for example, any steam or electric motor, but is usually an internal combustion motor, such as a gasoline, diesel, alcohol, propane, or otherwise powered internal combustion engine. A standard truck battery 7 is provided as a source of electric energy for starting the engine. An intake hose 8 is coupled to a source of fresh water, and a water pump or air compressor 9 driven by the power plant via V-belt (shown), direct drive, or otherwise for pressurizing the fresh water. One or more heat exchangers and associated plumbing 10 are coupled for receiving the pressurized fresh water and heating it. A recovery tank 11 is provided wherein gray water or soiled cleaning solution is stored after removal from the cleaned surface. A high pressure solution hose 12 is provided for delivering pressurized, hot water/chemical cleaning solution from the machine via a wand or cleaning tool 14 to the substrate to be cleaned, usually a carpet or hard flooring, and a chemical container 13 or other chemical system is coupled for delivering a stream of cleaning chemical additives into the hot water, typically as it enters the high-pressure solution hose 12. The wand or cleaning tool 14 is coupled to the high pressure solution hose 12 for receiving and dispersing the pressurized hot water/chemical cleaning solution to the carpet. The wand or cleaning tool 14 is the only “portable” part of truck-mount slide-in professional carpet cleaning systems 1 in that it is removed from the vehicle and carried to the carpet or other substrate to be cleaned, and it is the only equipment that makes physical contact with the carpet to be cleaned. A vacuum hose 15 is coupled to the wand or cleaning tool 14 for recovering the soiled water-based chemical cleaning solution from the cleaned surface via the wand or cleaning tool and delivering it to the recovery tank. Valves 16 and 17 control coupling of the hot water/chemical cleaning solution and recovery vacuum, respectively, to the wand or cleaning tool 14. The control valves 16, 17 may be either separate control valves (shown) or combined in a single control valve.
The slide-in or portable system 1 operates by delivering fresh water to an inlet to the system, utilizing either a standard garden hose or a fresh-water container. The system 1 adds energy to the fresh water, i.e., pressurizes it, by means of the pump or air compressor 9. The fresh water is pushed throughout the heat exchanger apparatus and associated plumbing 10 using pressure provided by either the pump or air compressor 9. The heat exchangers 10 gain their heat by thermal energy rejected from the power plant 4, e.g., from hot exhaust gases, coolant water used on certain engines, or another known means. On demand from the wand or cleaning tool 14, the heated fresh water is mixed with chemicals from the container 13 as the hot water is exiting the machine and entering the high-pressure hose 12. The hot water travels typically, but not limited to, between 50 feet to 300 feet to the wand or cleaning tool 14. The operator delivers the hot solution via the wand or cleaning tool 14 to the carpet or other surface to be cleaned and almost immediately extracts it along with soil that has been emulsified by thermal energy or dissolved and divided by chemical energy. The extracted, soiled water or cleaning solution is drawn via the vacuum hose 15 into the recovery tank 11 for eventual disposal as gray water.
It has been suggested that instead of using a separate heater for heating the cleaning liquid that waste heat from the internal combustion engine be used for that purpose. U.S. Pat. No. 4,593,753, granted Jun. 10, 1986 to P. J. McConnell for “EXHAUST GAS LIQUID HEATING SYSTEM FOR INTERNAL COMBUSTION ENGINES” discloses a system for heating water with exhaust gas heat. U.S. Pat. No. 4,109,340 granted Aug. 29, 1978 to L. E. Bates for “TRUCK MOUNTED CARPET CLEANING MACHINE” discloses a system in which the cleaning liquid is passed first through the cylinder block of a liquid cooled, internal combustion engine and then through a heat exchanger which also has engine exhaust gases passing therethrough. U.S. Pat. No. 4,284,127 granted Aug. 18, 1981 to D. S. Collier et al for “CARPET CLEANING SYSTEMS” discloses a similar system which directs the cleaning liquid through a first heat exchanger into which the liquid engine coolant also is directed. The preheated cleaning liquid then passes through a second heat exchanger where it extracts heat from the engine exhaust gases.
In all of the aforementioned systems in which the cleaning liquid is directed in heat exchange relationship with the exhaust gases of the internal combustion engine there is a danger that the cleaning liquid could become overheated. To avoid damage to surfaces to be cleaned the temperature of the cleaning liquid, as a general rule, should not exceed 250 degrees F. Internal combustion engine exhaust gases can reach temperatures as high as 1650 degrees F. With the engine running and a low flow rate for the cleaning liquid the latter can rapidly be heated to an undesirably high temperature in the exhaust gas heat exchange.
One attempt at a solution for controlling the cleaning liquid temperature is disclosed by U.S. Pat. No. 3,594,849 granted Jul. 27, 1971 to C. L. Coshow for “CLEANING APPARATUS” which provides a cleaning system in which air and heated cleaning fluid recovered from a carpet is conveyed in heat exchange relationship with cleaning liquid being conveyed to the carpet.
More typically, a thermostatically controlled dump valve is incorporated for dumping the overheated cleaning liquid before it can reach the surface to be cleaned. One such dumping arrangement is described hereinafter and in the aforementioned U.S. Pat. No. 4,940,082 granted Jul. 10, 1990 to James R. Roden for “CLEANING SYSTEM,” the complete disclosure of which is incorporated herein by reference. U.S. Pat. No. 4,940,082 also disclosed utilization of the heat contained in the return air stream after it passed through the vacuum pump. Because the vacuum pump adds a significant quantity of heat to this air stream useful heat can be obtained from its exhaust and imparted to the cleaning liquid being heated. However, U.S. Pat. No. 4,940,082 offered no suggestions for preventing overheating of the cleaning liquid in heat exchange relationship with the engine exhaust gases.
U.S. Pat. No. 4,991,254 granted Feb. 12, 1991 to Roden, et al. for “CLEANING SYSTEM,” the complete disclosure of which is incorporated herein by reference, disclosed extracting heat both from the exhaust gases of an internal combustion engine and the air exiting a vacuum pump to heat the cleaning liquid. Heat from these two sources was mixed before imparting it to the cleaning liquid by mixing the exhaust gases and the air from the vacuum pump before placing the mixture in heat exchange relationship with the cleaning liquid. U.S. Pat. No. 4,991,254 also disclosed utilizing heat from a cooling system for the internal combustion engine to further heat the cleaning liquid. A thermostatically controlled dump valve in a high pressure hose at the exit of second heat exchanger prevents delivery of too high temperature cleaning liquid to the cleaning wand. The dump valve detects cleaning liquid temperature in excess of 250 degrees F and opens, thereby dumping the over heated cleaning liquid into waste tank until the cleaning liquid at the exit from heat exchanger again has a temperature within the desired range.
However, in some applications it would be desirable to avoid wasting the unused cleaning liquid by dumping it when it gets too hot.